This invention relates to control of incompetent subterranean formations penetrated by wellbores.
In the production of fluids, such as oil, gas, water, etc, from subterranean formations, a number of difficulties are encountered when the well through which the fluids are produced penetrates an incompetent or unconsolidated subterranean formation. Such formations frequently are composed of incompetent sand, and the grains of the sand become entrained in the fluid being produced and are carried into the wellbore. The result of such entrainment, among other things, is the abrasion of the pumping equipment in the wellbore, clogging of the strainers, sand bridging in the tubing, plugging of surface flow lines, filling of oil-water separators, and the sanding in of the cavity immediately adjacent the strainers. These results, in turn, ultimately cause a sharp decrease in the rate of production of hydrocarbon fluids and increased maintenance costs.
Various solutions to this problem have been proposed. For example, gravel and sand packs employing the injection of particulate solids in thickened hydrocarbons wherein the thickening agent is an aluminum soap of fatty acids, finely-divided silica, bentonite, certain other soaps (NAPALM) and the like have been employed as are disclosed by U.S. Pat. Nos. 2,906,338, 2,978,024, 3,498,380 and 3,064,730.
One of the more successful solutions to the incompetent formation problem has been the use of polymeric resins for injection into the wellbore in combination with solid particulate matter to form a consolidated area adjacent the wellbore in the sand producing zone. Such techniques are shown in U.S. Pat. No. 3,378,071, patented Apr. 16, 1968, by Derry D. Sparlin and assigned to Continental Oil Company as well as U.S. Pat. No. 3,692,116 by Derry Sparlin and assigned to Continental Oil Company. U.S. Pat. No. 3,378,071 and U.S. Pat. No. 3,692,116 are hereby incorporated by reference.
Gelled water systems are presently used for placing gravel and plastic against subterranean formations for controlling incompetent sand. It is desirable in many instances to use a gelled oil system in many formations wherein the oils are more compatible with the subterranean environment than water. Water in some formations impairs the production of fluids from the well by forming emulsions with the oil in the formation, hydrating shales or clays in the formation and the like. Gelled oil prevents these problems and is diluted by the produced crude oil which facilitates the initial production of oil from the well after well treatment.
A further patent relating to a similar process is U.S. Pat. No. 3,391,738, patented July 9, 1968, by Derry D. Sparlin and assigned to Continental Oil Company. U.S. Pat. No. 3,391,738 is hereby incorporated by reference.
In such processes, the mixture injected into the formation to consolidate the portions of the subterranean formations surrounding the wellbore comprises a polymeric resin which polymerizes in situ and, in many instances, contains particulate material. In the use of such processes, it has long been considered desirable that a gelled oil, or the like, be available for suspending the sand and unpolymerized resins during injection into the wellbore. Such a gelled oil has been unavailable to the art heretofore, since the gelling agents commonly used have been found to be incompatible with the polymeric resins injected. As a result, the art has used viscous oils and the like to suspend the particulate matter in solution with the polymeric resins.
The use of viscous oils and the like results in difficulty in removing the viscous oil from the formation once the resins have polymerized. Accordingly, considerable time has been devoted to attempted development of gelled oil mixtures which are capable of suspending the particulate matter for injection into the wellbore in solution with the polymeric resins without adversely affecting the performance of the resins.